Beryllium is the dominant plasma-facing component proposed for ITER. A series of experiments have been conducted in the PISCES-B device to investigate the erosion and hydrogen retention characteristics of beryllium. The sputtering yield is observed to be strongly influenced by trace amounts ( 1%) of intrinsic plasma impurities. At low sample exposure temperatures (below 2500C), the beryllium surface remains relatively free of contaminants and a sputtering yield similar to that of beryllium-oxide is measured. At higher sample exposure temperatures, impurities deposited on the beryllium surface can diffuse into the bulk beryllium and can thereby reduce their chance of subsequent erosion. These impurities form a surface layer mixed with beryllium which exhibits a reduced sputtering yield. Both elemental and chemical depth profile analysis have been conducted on the plasma exposed samples to determine the composition and chemical bonding structure of the impurity layer.

In addition, the hydrogen isotope retention characteristics of beryllium under ITER first wall (exposure temperature = 2000C, ion flux = 1 x 10²¹ m^-2 s^-1, ion bombardment energy = 100 eV) and baffle (exposure temperature = 5000C, ion flux = 1 x 10²² m^-2 s^-1, ion bombardment energy = 100 eV) conditions has been investigated. The quantity of deuterium retained in the samples saturates above a fluence of 10²³ m^-2 at about 4 x 10²⁰ m^-2 for the 2000C exposure and at 2 x 10²⁰ m^-2 for the 5000C case. Thermal desorption spectroscopy (TDS) has been used to measure the release temperature of the retained deuterium. The TMAP computer code has been used to model the release characteristics of the plasma exposed beryllium.

* Work supported under DOE grant # DE-FG03-95ER-54301.